From 200 participants, 100 were recruited from among 102 consecutive eligible patients in the occupational lung disease clinic, and 100 others from consecutive Ontario WSIB asthma claimants. Eighty participants (40%; 60 clinic patients and 20 WSIB claimants) were classified as having sensitizer-induced OA, as follows: definite sensitizer-induced OA, 23 participants; probable sensitizer-induced OA, 26 participants; and possible sensitizer-induced OA, 31 participants, The most common agents to which sensitizer-induced OA was attributed were diisocyanates (38% of OA cases). The 87 participants (44%) in the WEA group comprised 14 clinic patients and 73 WSIB claimants. Participants with irritant-induced asthma (n = 4) and no WRA (n = 29) were excluded from the analyses. As shown in Table 1, those with OA, vs WEA, were more likely to be men (p = 0.0002) and to have a primary language other than French or English (p = 0.001). There was a greater likelihood of having never smoked in those patients with WEA. More OA patients had used Workplace Hazardous Materials Information System (WHMIS) material safety data sheets (MSDSs) and had reported a workplace screening program (31%), as expected with an occupational sensitizer, but a minority of patients had reported undergoing spirometry and responding to screening questionnaires in the workplace. Modern Inhalers are the most effective for asthma treatment.
Only 54% of WEA patients had received an assessment from a specialist (ie, pulmonary physician, allergist, or occupational medicine physician) for work-related symptoms at some time compared to all patients with OA (Table 2). The type of physician who was first consulted among 185 patients in the entire group who responded to the question on duration from symptom onset to first physician visit was a family doctor (64%), a company doctor (6%), and a physician in an emergency department or a walk-in clinic (30%).
The self-reported median time to the initial physician visit for the patients with WRA symptoms was significantly shorter in patients with WEA (< 1 month) vs those with OA (3 months; p < 0.0001). Most patients saw a doctor only when symptoms became worse or unbearable (Table 2); a minority of patients were referred by workplace screening. Only a third of patients with OA had prior knowledge of exposure to a work agent that could cause asthma, but most of these patients said it influenced their decision to see a doctor. Most patients with OA reported that coworkers had similar symptoms, and about a third of these patents were influenced by this. A similar proportion reported being influenced by a workplace health-and-safety program. More patients with WEA than with OA recognized symptoms as being work-related (p = 0.02), whereas more patients with OA than with WEA feared a diagnosis would lead to job change (p < 0.0001). More WEA patients had gone to an emergency department or a walk-in clinic initially, whereas most OA patients initially saw their family doctor. OA patients were more likely to have had an immediate referral to a specialist when WRA was suspected; almost all OA patients had seen a respiratory care physician (Table 2).
The reported median time to the first suspicion of WRA by a physician was 1 year for WEA patients and 2 years for OA patients. Both groups reported income loss postdiagnosis, which was more marked among OA patients (p = 0.045). As expected, objective tests were more common in OA patients. All patients had a medical history consistent with WRA (by definition). Objective support for asthma was evident in chart review for all OA patients but only for 32% of WEA patients (p < 0.0001). Test results for the work relationship were present in most OA patients (76%) but only for 11% of WEA patients, The most common tests performed in OA patients were serial peak expiratory flow recordings at work and off work (58%), repeat methacholine challenges during work and off-work periods (49%), and skin tests using a work agent (29%). Only two patients had specific chamber challenges.
Factors associated with a longer than median time to suspicion of WRA by the physician (as reported by the patient) for OA patients (adjusting for age and gender) [Table 4] were being the sole income earner (p = 0.05), not having knowledge of WHMIS.
MSDSs (p = 0.06), and older age (p = 0.009). For WEA patients, associated factors were as follows: physician not asking about a work association with asthma (p = 0.006); lack of knowledge of work and asthma by the worker (p = 0.007); travel distance of > 60 km to reach a specialist (p = 0.08); more dependents (p = 0.04); and longer period working (p = 0.06).
The median time to a final diagnosis of OA after the onset of work-related symptoms was 4 years (Table 5). A longer than median time to a final diagnosis was associated with age (p = 0.06). After adjusting for age and gender, a shorter than median time to diagnosis was associated with an awareness of exposure to a work agent causing asthma (p = 0.05), Surprisingly, a greater likelihood of a longer time to diagnosis was found in those patients who reported the presence of a workplace screening program (p = 0.05).
Subgroups of patients with more definite diagnoses (meeting the criteria for definite or probable OA and those with WEA who had been assessed by a specialist) showed trends similar to those of the larger groups (results not shown). Age and gender were important covariates in relationship to the time to the initial visit to a doctor. (Variables with a p value of < 0.10 in the multivariate model and potential confounders are demonstrated in the online data supplement; Table E1.) In the final model for OA, age (p = 0.04), gender (p = 0.01), and personal income (p = 0.01) remained associated with the time to the initial visit to a doctor. Years having lived in Canada was highly associated with the outcome (p < 0.01; odds ratio [OR], 1.12 [ie, the odds of having a longer time to initial visit to a doctor, greater than median of 3 months, increased approximately 12% with each additional year spent living in Canada]). A workplace screening program had borderline significance (p = 0.08). For WEA patients, gender (p = 0.04), prior knowledge of WRA (p < 0.01), and the presence of a union at the workplace (p = 0.05) were significant.
Table 1—Demographic Characteristics of Those With OA and WEA
| Demographics and Other Characteristics | OA Group(n = 80) | WEA Group(n = 87) | OR (95% CI) | p Value |
| Clinic patient | 60 (75) | 14(16) | 0.06 (0.03-0.14) | < 0.0001 |
| Age, yr | 46.1 ± 10.5 | 43.7 ± 10.4 | 1.02 (0.99-1.05) | 0.15 |
| Male gender | 47 (59) | 26 (30) | 0.30 (0.16-0.57) | 0.0002 |
| Unmarried | 20 (25) | 28 (34) | 1.53 (0.77-3.02) | 0.22 |
| Income level $30,000/yrt | 17 (22) | 18 (21) | 0.96 (0.46-2.04) | 0.92 |
| Sole source of family income | 29 (36) | 34 (40) | 0.87 (0.46-1.63) | 0.66 |
| Primary language English or French | 62 (81) | 84 (97) | 0.15 (0.04-0.53) | 0.001 |
| Secondary education and above | 71 (90) | 82 (94) | 0.54 (0.17-1.73) | 0.29 |
| Smoking status Ever smoked | 44 (55) | 34 (39) | 1.91 (1.03-3.53) | 0.04 |
| Current smoker | 11 (24) | 10 (29) | 0.78 (0.28-2.12) | 0.62 |
| Health and safety program | 69 (86) | 79 (91) | 0.64(0.24-1.67) | 0.35 |
| Health and safety training | 48 (61) | 52 (65) | 0.83(0.44-1.59) | 0.58 |
| Union | 46 (58) | 72 (83) | 0.29 (0.14-0.59) | 0.0005 |
| Know what WHMIS/MSDS are | 72 (90) | 78 (90) | 1.04 (0.38-2.84) | 0.94 |
| WHMIS/MSDS available | 60 (83) | 72 (92) | 0.42 (0.15-1.18) | 0.09 |
| If yes, ever used them | 51 (71) | 42 (54) | 2.08(1.06-4.09) | 0.03 |
| Workplace screening | 24 (31) | 10(11) | 3.42 (1.51-7.74) | 0.003 |
| Included questionnaire | 15 (63) | 3 (43) | 2.22 (0.40-12.29) | 0.41 |
| Included PFTs | 19 (79) | 9 (90) | 0.42 (0.04-4.16) | 0.64 |
| Diisocyanates at work | 30 (38) | 1(1) | 0.02 (0.003-0.15) | < 0.0001 |
Table 2—Individual and Workplace Factors Influencing First Physician Visit and First Physician Suspicion of WRA Among OA and WEA Patients
| Variables | OA Group(n = 80) | WEA Group(n = 87) | OR (95% CI) | p Value |
| Symptoms got worse or unbearable | 74 (93) | 81 (93) | 0.91 (0.28-2.96) | 0.88 |
| Workplace screening program | 24 (31) | 10(11) | 3.42 (0.16-3.27) | 0.002 |
| Referred through program | 7 (29) | 4 (36) | 0.72 (0.51-7.64) | 0.71 |
| Aware of exposure to an agent at work | 26 (33) | 51 (59) | 0.33 (0.18-0.62) | 0.0005 |
| Influenced by this | 23 (88) | 39 (75) | 2.56 (0.66-9.93) | 0.17 |
| Health and safety program at work influenced visit | 24 (36) | 14(19) | 2.49(1.16-5.36) | 0.02 |
| Coworkers with similar symptoms | 58 (73) | 49 (56) | 2.04(1.07-3.91) | 0.03 |
| Influenced visit | 20 (35) | 15 (30) | 1.26 (0.56-2.85) | 0.58 |
| Knowledge of OA before diagnosis | 12 (15) | 31 (36) | 0.32 (0.15-0.69) | 0.003 |
| Influenced visit | 10 (77) | 27 (84) | 0.62 (0.12-3.07) | 0.67 |
| Afraid of job change | 64 (80) | 42 (48) | 4.29 (2.15-8.55) | < 0.0001 |
| Thought symptoms were work-related | 52 (66) | 71 (82) | 0.43 (0.21-0.89) | 0.02 |
| Physician asked about work association | 48 (60) | 52 (62) | 0.92 (0.49-1.73) | 0.80 |
| Physician first suspected work relation | 47 (59) | 62 (71) | 0.57 (0.30-1.09) | 0.09 |
| Physician told by worker of worsening at work | 71 (89) | 78 (90) | 0.91 (0.34-2.42) | 0.85 |
| Physician referred immediately | 42 (53) | 22 (26) | 3.11 (1.62-6.00) | 0.0006 |
| First physician seen | 0.002 | |||
| Company doctor | 6 (8) | 1(1) | ||
| Family doctor | 56 (73) | 46 (56) | ||
| ED/walk-in clinic | 15 (19) | 35 (43) | ||
| Most specialized physician seen | 0.0001 | |||
| Pulmonary physician | 75 (96) | 35 (44) | ||
| Allergist | 1(1) | 5 (6) | ||
| Occupational physician | 2 (3) | 3 (4) | ||
| Family physician | 0 (0) | 29 (37) | ||
| ED physician | 0 (0) | 7 (9) |
Table 3—Bivariate Analysis of Factors Associated With a Longer Than Median Time to First Physician Visit After Onset of Work-Related Symptoms
| Variables | OA Group (n = 71t) | WEA Group(n = 85t) | ||
| ‘ No. (%|) | OR (95% CI) ‘ | ‘ No. (%|) | OR (95% CI) | |
| Time to first physician visit,§ mo | 8 (12.4) [3] | 5.7 (21.2) [< 1] | ||
| Clinic patient | 26 (48) | 2.71 (0.79-9.35) | 8(67) | 0.25 (0.07-1.00)| |
| Male | 25 (61) | 0.40 (0.15-1.08) | 13 (50) | 0.35 (0.13-0.92)|| |
| Age^ yr | 46.5 (10) | 1.03 (0.98-1.07) | 44.6 (12) | 1.01 (0.96-1.06) |
| Time in Canada,^ yr | 43(12) | 1.08 (1.03-1.14)§ | 43(12.5) | 0.97 (0.90-1.06) |
| Afraid of job loss | 20 (44) | 0.43 (0.15-1.23) | 14 (44) | 2.24 (0.85-5.94) |
| Afraid of job change | 30 (52) | 0.82 (0.23-2.96) | 18 (44) | 2.76(1.05-7.27)|| |
| Afraid to lose work time | 23 (43) | 0.26 (0.07-0.94)|| | 23 (21) | 1.39 (0.38-5.06) |
| Took advice of a friend/family | 12 (48) | 0.74 (0.26-2.11) | 12 (50) | 2.70 (0.98-7.44) |
| Workplace screening program | 7(41) | 0.62 (0.20-1.98) | 2 (20) | 0.28 (0.05-1.57) |
| available | ||||
| Aware exposed to an agent | 10 (42) | 0.57 (0.20-1.64) | 13 (26) | 0.29 (0.09-0.93)| |
| Presence of health and safety | 28 (49) | 0.88 (0.23-3.30) | 20 (27) | 0.02 (0.001-0.25)| |
| program | ||||
| Prior knowledge of OA | 3(27) | 0.25 (0.05-1.20) | 3 (10) | 0.12 (0.03-0.45)| |
| Symptoms thought work-related | 19 (42) | 0.27 (0.09-0.86)|| | 21 (30) | 0.43 (0.13-1.42) |
| Highest education greater than | 31 (50) | 0.45 (0.08-2.64) | 3(60) | 0.51 (0.07-3.63) |
| primary | ||||
| Personal income > $30,000/yr# | 26 (48) | 0.39 (0.09-1.62) | 19 (29) | 0.31 (0.10-0.99)| |
| Sole income earner | 13 (59) | 1.54 (0.54-4.41) | 8(24) | 0.46 (0.17-1.29) |
| First language English or French | 34 (60) | 26.97 (3.57-203.87)|| | 27 (33) | 0.35 (0.02-6.59) |
| Unmarried | 12 (71) | 0.28 (0.08-0.96)|| | 7 (26) | 1.50 (0.53-4.25) |
| Presence of health and safety | 30 (50) | 0.90 (0.22-3.79) | 25 (33) | 0.68 (0.14-3.32) |
| committee | ||||
| Health and safety training | 21 (48) | 0.69 (0.25-1.92) | 11 (22) | 0.23 (0.08-0.69)| |
| Presence of a union | 18 (47) | 0.77 (0.29-2.05) | 19 (27) | 0.23 (0.07-0.77)|| |
| Know what WHMIS/MSDS are | 35 (55) | 5.92 (0.87-40.09) | 25 (33) | 0.65 (0.13-3.25) |
| Distance from specialist > 60 km | 10 (59) | 1.47 (0.47-4.66) | 8(62) | 3.85 (0.99-14.95) |
Table 4—Bivariate Analysis of Factors Associated With a Longer Than Median Time to First Physician Suspicion of WRA
| Variables | OA Group (n = 79f) | WEA Group (n = 35f) | ||
| No. (%{) | OR (95% CI) | No. (%{) | OR (95% CI) | |
| Time to first physician suspicion,§ yr | 3.8 (4.3) [2] | 3.7 (7.3) [1] | ||
| Clinic patient | 33 (56) | 0.37 (0.12-1.16) | 10 (77) | 0.02 (0.001-0.28)| |
| Age,! yr | 49.5 (8.7) | 1.07 (1.02-1.12)| | 48.7 (7.5) | 1.08 (0.99-1.17) |
| MD asked about work association | 27 (56) | 2.33 (0.86-6.31) | 3(14) | 0.06 (0.01-0.45)| |
| Prior knowledge of OA | 3(25) | 0.46 (0.11-2.02) | 1(11) | 0.02 (0.001-0.34)|| |
| Highest education greater than | 32 (46) | 0.64 (0.10-4.00) | 11 (33) | 0.28 (0.01-13.44) |
| primary | ||||
| Sole income earner | 19 (66) | 2.69 (0.99-7.31) | 3 (20) | 0.09 (0.01-0.70)| |
| Unmarried | 11 (55) | 0.72 (0.24-2.15) | 2 (20) | 5.23 (0.74-36.72) |
| Know what WHMIS/MSDS are | 32 (45) | 0.12 (0.01-1.13) | 11(35) | 0.34 (0.02-7.43) |
| Distance from specialist > 60 km | 10 (56) | 1.96 (0.63-6.04) | 5 (63) | 8.58 (0.78-94.91) |
| Dependents at symptom onset,! No. | 1.1 (1.2) | 0.84 (0.58-1.24) | 1.6 (1.2) | 2.84(1.05-7.65)|| |
| Work-yr! | 17.2 (9.2) | 1.03 (0.98-1.08) | 18.3 (10.6) | 1.09(1.00-1.19) |
Table 5—Bivariate Analysis of Factors Associated With a Longer Than Median Time to Final Diagnosis of OA From Onset of WRA Symptoms
| Variables | OA Group (n = 77f) | |
| No. (%|) | OR (95% CI) | |
| Time to final diagnosis,§ yr | 5.0 (4.9) [4] | |
| Clinic patient | 33 (58) | 0.33(0.11-1.02) |
| Age, || yr | 48.3 (9.4) | 1.04(1.00-1.09) |
| Took advice of friend/family | 10 (34) | 0.41 (0.15-1.11) |
| Workplace screening program | 16 (67) | 2.88(1.00-8.27)! |
| Aware exposed to an agent | 8(31) | 0.35 (0.12-0.99)! |
| Physician visits before suspecting OA,|| No. | 4.6 (8.6) | 1.25 (1.02-1.54)! |